Conventional sootblowers of the long retracting type include a lance tube which is moved along a horizontal path several feet in length. During the traveling motion of the lance tube it may be rotated about its longitudinal axis and a cleaning fluid discharged through one or more nozzles mounted on its forwardmost end. The fluid may be directed against various internal surfaces of the boiler to remove undesirable soot accumulations, rust, corrosion and the like.
Fluid is fed to the lance tube by a coaxially aligned feed tube. The lance tube circumscribes the feed tube. Fluids such as steam, water, detergent and mixtures thereof are delivered from one end of the feed tube to the other and then into the lance tube for discharge from the nozzles.
Various means have been suggested in the prior art for imparting movement to the lance tube and guiding it along its lengthy path as it enters and leaves the boiler. Examples of the insertion apparatus are illustrated in U.S. Pat. Nos. 4,437,201; 4,498,213; and 5,267,533. The particular means for inserting and retracting the lance tube are unrelated to the inventive concept described herein. Any of the disclosed insertion systems may be used without departing from the spirit of the inventive concept to be described subsequently. Indeed, other insertion apparatus and procedures may be incorporated using the inventive concept to be described which have not yet been disclosed in those patents. Such undisclosed apparatus would not depart from the spirit of the invention disclosed herein because this invention is concerned with the sealing structure between tubes rather than how the tubes move.
This invention is concerned with the configuration of the sealing assembly between the supply or feed tube and the lance tube of sootblower apparatus. Conventionally, a lance tube and a supply tube are concentrically mounted with the supply tube connected to a source of fluid such as steam or water under suitable pressure. The concentrically mounted lance tube is mounted at its rear most area with a carriage which supports the rear end and drives it in and out of the boiler or other heat transfer apparatus in a particular pattern. Examples of such rear mounting structure are illustrated in U.S. Pat. Nos. 2,185,450; 4,437,201; 5,090,087; and 5,277,153.
With each carriage it is conventional to have a stuffing box containing a deformable packing material which is compressed and deformed by a follower gland to provide a fluid tight seal between the external surface of the supply tube and the internal surface of the lance tube. It is well known to provide a yoke type flange structure on the rear surface of the follower gland which cooperates to maintain deforming pressure on the packing. FIGS. 1 and 2 illustrate such prior art.
In FIG. 1, a supply tube 10 is concentrically mounted about axis 12 with a lance tube 14. Lance tube 14 is illustrated as being somewhat thicker than supply tube 10 but this is misleading. The illustrated rear portion of lance tube 14 may be characterized as a hub and it may have attached thereto various flanges, gears and the like, including a roller bearing 16. During its rotation as it is advanced and retracted from the boiler by apparatus which is attached to its rear or hub end it delivers a cleaning fluid under pressure.
Mounted within a stuffing box 18 formed in the internal surface of lance tube 14 is a deformable packing 20 which forms a seal between the internal surface of lance tube 14 and the external surface of supply tube 10. Its function is to prevent the escape of cleaning fluid fed to the inside of lance tube 14 by supply tube 10. Thereby the only escape for the injected fluid is through the nozzle structure (not shown) on the forward end of the lance tube 14.
To prevent the packing 20 from escaping the stuffing box 18, a suitably off-set forward bushing 22 engages the forward end of packing 20. The rear or trailing end of the packing 20 is engaged by a cylindrical follower gland 24. Cylindrical gland 24 includes a yoke or segmented flange 26 having a pair of slots 28, 30 extending through flange 26 at diagonally opposite locations, see FIG. 2.
Studs 32, 34 are threaded into apertures 36, 38 formed in the rear end of lance tube 14. To compress and deform packing 20, the follower gland 24 is urged forward by nuts 42 tightened on the exposed ends of studs 32, 34 to engage flange 26 and drive the gland forward.
As illustrated in FIG. 1, a cylindrical washer 40 fits over each stud 32, 34 and is tightened against yoke 26 by a nut 42. To prevent nut 42 from being loosened due to vibration and the like during sootblowing operations, a locknut 44 is threaded into place to engage each tightening nut 42.
At preselected periods of time or when a leak occurs in packing 20, locknuts 44 are retracted and tightening nuts 42 are tightened against yoke 26 to urge gland 24 forward to further compress packing 20 and reseal the annulus against leakage.
The problem this creates is a lack of uniform pressure on packing 20 to maintain a uniform degree of compression. It is desirable to have a uniform application of force to such packing which will not require the manual operation just described to reseal a leak. Various solutions have been suggested to achieve this desired automatic tightening result and many involve one or more springs to achieve this constant bias against the trailing gland. Examples are illustrated and described in U.S. Pat. Nos. 2,185,450; 2,287,207; 3,011,808; 3,659,862; 3,968,970; 5,090,087; and 5,267,533.